Technical term for "combination effect"

#1
Hello everybody,

For the critics of my bachelor thesis I want to point out that my findings only apply for the used parameters and "combination effects" have not been tested.

I am not sure whether combination effect is the right word.

One example for the effect I mean:
I want to meausre the effect of the temperature on ice-cream and the effect of distance to a lake of the ice-cream stand.

2 Tests:
1. Temperature = perfect sunny summer day, Distance: Varying from 100 meter to 5,000 meter. (Result: The shorter the distance to the lake, the higher the revenues)
2. Temperature = super super desert hot so that everybody keeps in their homes and no-one goes to the lake, Distance: Varying from 100 meter to 5,000 meter. (Result: The shorter the distance to the lake, the lower the revenues)

So without testing the second case, the relationship distance and sales would be wrong. In combination with different weather, the relationship is positive for medium to hot temperatures and negative for very hot temperatures.

How is the right term for this effect?